This invention relates generally to artillery and more specifically to howitzers employing expendable breech guns to provide lightweight, rapid fire howitzers.
In conventional gun mechanism operation a significant portion of the total cycle time is usually given over to ramming a round into the chamber, positioning and locking the breechblock behind the round, unlocking and repositioning the breechblock after firing, and extracting the spent case from the chamber. in an expendable breech gun the cartridge case is designed to be sufficiently strong to withstand maximum breech pressure without external support. Such a case can therefore take on the function of the conventional gun chamber, serving as a one-shot breech, provided an appropriate seal is maintained between the case and the barrel while firing. The expendable breechcase can be made in the form of a simple right circular cylinder which encloses both the projectile and the propellant chamber and is open at the forward end. Low density filament-wound fiberglass/epoxy composite materials are expected to provide high specific strength at low cost in this application.
In operation the expendable breech round is mechanically locked in alignment with the barrel, supported from behind, and fired electrically. A dynamic gas seal may be maintained between the forward end of the breechcase and the face of the barrel for the duration of the pressure pulse by means of a V-shaped, plated metal, spring type ring seal bonded to the forward end of the case. The chief advantage of the expendable breech round arises from the fact that it can be positioned, fired and ejected in a single feed direction, thus eliminating conventional ramming and extraction functions as well as the mechanisms required for their accomplishment. While significantly reducing the overall mechanical complexity of the gun mechanism, the expendable breech approach also tends to produce a higher rate of fire because the number of mechanical operations are reduced and therefore less time is required to cycle each round through the gun mechanism.